title: Positive end-expiratory pressure influences echocardiographic measures of diastolic function: a randomized, crossover study in cardiac surgery patients.
abstract: BACKGROUND
  Ultrasonography of the cardiovascular system is pivotal for hemodynamic assessment. Diastolic function is evaluated with a combination of tissue Doppler (e' and a') and pulsed Doppler (E and A) measures of transmitral- and mitral valve annuli velocities. However, accurate echocardiographic evaluation in the intensive care unit or perioperative setting is contingent on relative resistance to positive pressure ventilation and changes in preload. This study aimed to evaluate the effects of positive end-expiratory pressure (PEEP) and positioning on echocardiographic measures of diastolic function.
  
  
  METHODS
  The study was a prospective, randomized, crossover study. Cardiac surgery patients with ejection fraction greater than 45% and averaged e' of 9 or more were included. Postoperatively, anesthetized patients were randomized into six combinations of PEEP (0, 6, 12 cm H2O) and positions (horizontal, Trendelenburg). At each combination, e' (primary endpoint), a', E, and A were obtained with transesophageal echocardiography along with left ventricular area. Image analysis was performed blinded to the protocol.
  
  
  RESULTS
  Thirty patients completed the study. PEEP decreased lateral e' from 6.6±3.6 to 5.3±3.0 cm/s (P<0.001) in the horizontal position and from 7.4±4.2 to 6.5±3.3 cm/s (P<0.001) in Trendelenburg. Similar results were found for septal e', a' bilaterally and transmitral pulsed Doppler measures, and PEEP decreased left ventricular area. E/A, E/e', and e'/a' remained unaffected by PEEP and positioning.
  
  
  CONCLUSIONS
  When evaluating diastolic function by echocardiography, the levels of PEEP and its effect on ventricular area have to be taken into account. In addition, this study dissuades the use of E/e' for tracking changes in left ventricular filling pressures in cardiac surgery patients.
authors.affiliation: * Research Assistant, † Medical Student, ‖ Professor, Department of Anaesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark, and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark. ‡ Research Nurse, § Associate Professor, Department of Anaesthesiology and Intensive Care, Aarhus University Hospital.
authors.forename: Peter
authors.initials: P
authors.lastname: Juhl-Olsen
authors.forename: Johan Fridolf
authors.initials: JF
authors.lastname: Hermansen
authors.forename: Christian Alcaraz
authors.initials: CA
authors.lastname: Frederiksen
authors.forename: Linda Aagaard
authors.initials: LA
authors.lastname: Rasmussen
authors.forename: Carl-Johan
authors.initials: CJ
authors.lastname: Jakobsen
authors.forename: Erik
authors.initials: E
authors.lastname: Sloth
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D006348:Cardiac Surgical Procedures / Q000379:methods*; D018592:Cross-Over Studies; D003971:Diastole / Q000502:physiology*; D017548:Echocardiography, Transesophageal / Q000379:methods*; D005260:Female; D018475:Head-Down Tilt; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D015588:Observer Variation; D056888:Patient Positioning; D011175:Positive-Pressure Respiration; D011184:Postoperative Period; D011446:Prospective Studies; D018401:Sample Size; D016896:Treatment Outcome